Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758430Ab2EJOpx (ORCPT ); Thu, 10 May 2012 10:45:53 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:57376 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1756518Ab2EJOpv (ORCPT ); Thu, 10 May 2012 10:45:51 -0400 Date: Thu, 10 May 2012 10:45:50 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: NeilBrown cc: Peter Chen , Samuel Ortiz , Felipe Balbi , Grazvydas Ignotas , Greg Kroah-Hartman , , , Subject: Re: [PATCH 0/6] twl4030: Various fixes for charing-from-USB In-Reply-To: <20120510123754.6a6d95b9@notabene.brown> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1283 Lines: 32 On Thu, 10 May 2012, NeilBrown wrote: > Maybe we need to not suspend the USB OTG interface when the device as a > whole enters suspend-to-RAM. Maybe we need to register a dummy gadget to > the bus active while in suspend? > Does the gadget have to be responsive while-ever the bus is not suspended? Yes. > Maybe we can arrange for any USB activity to trigger a resume? Probably not, at least, not fast enough. The gadget is required to respond to USB packets within a few microseconds. At a minimum, the USB device controller would have to remain fully powered. > Entering suspend while still charging really should be possible - at least > with a dump charger and hopefully from a host port as well. I'll like to > find the best way to achieve that, and any help you can provide would be > greatly appreciated. If the gadget is attached to a dumb charger rather than a host then there's no problem. But otherwise it's not so simple. Have you read the USB charger class specification? (I haven't...) Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/